Two year ago: Openvpn was fine, but webpages of providers were blocked (not a bad strategy...).
Last year: private Openvpn server worked, but connections dropped after ~1Gbyte was transferred, and well known providers were blocked
This year: openvpn was detected (not sure how!) and private server seems to have ended on some "gray" list, ssh connectionsafter that were very slow (although that could coincide with slow internet); sshing to singapore AWS cloud was fine, but i had the feeling that switching between ports for ssh helped after big data transfers or long conenctions. Connecting by mobile (state telecom) was better than by WLAN.
Blocking seems to happen solely based on target (outside China) IP.
The rationale behind blocking vpns but not ssh is simple: China is not interested in blocking perfectly. They don't care about (or even may like) that you can set up cloud servers which you need for your thing outside China. They dont care about 1% of the population and all foreigners getting unfiltered access to the outside world. As long as they can filter the information for the vast majority. Which implies that the material they mostly care about is video, which means that intentionally slowing ssh still enable you to do your admin work, but you can not copy 1000 youtube videos quickly. Also, for ssh there is no "1-click-vpn" client available......